A technology that estimates an age of a customer by recognizing a face image of the customer is known. However, it is difficult to accurately estimate the age of customer from the face image. Therefore, it is difficult to automatically perform checkout of age-restricted merchandise (alcoholic beverages and cigarettes) based on the face image. Alternatively, a cashier may subjectively estimate a customer class (age, sex, ethnicity, and the like) of the customer. However, it is still difficult to accurately estimate the customer class.